Conventionally, techniques of estimating an energy saving effect derived from an implementation of an energy saving control to facilities in view of environmental parameters such as a weather condition have been proposed. For example, Patent Literature 1 discloses a method of estimating an energy saving effect by evaluating a difference between an actual power consumption amount measured in facilities prior to the implementation of the energy saving control and a converted power consumption amount obtained by correcting the actual power consumption amount measured in facilities posterior to the implementation of the energy saving control in view of a weather condition.